The invention relates to a filling assembly for volumetric metering of finely divided powder, in particular of medicinal powders for pulmonary administration, comprising a filling device and a metering container with an interior and with a rim circumferentially extending about a fill opening of the metering container, wherein the filling device comprises a cover and at least one filling line passing through the cover, wherein the cover, when filling the metering container, covers the fill opening and the rim, and wherein the filling line, when filling the metering container, opens into the interior. The invention also relates to a method for operating such a filling assembly.
Small quantities of powder, in particular small quantities of medicinal powder or powdery medication, for example, for pulmonary or for transdermal administration, must be metered and packaged in individual doses of a few milligrams or even micrograms suitable for the user. Such metering by weighing is difficult for which reason it is common in such applications to employ volumetric metering.
A known form of volumetric metering is done with a so-called membrane metering device disclosed, for example, in WO 2009/046728 A1. In this connection, a metering container for receiving the powder is provided, for example, in the form of a blister pack or the like with an interior, with a fill opening, and with a rim circumferentially surrounding the fill opening. A filling device that is matched thereto has a cover in the form of an air-permeable membrane that, when filling the metering container, covers the fill opening and its rim. Moreover, a filling line for the powder is provided that passes through the membrane and opens within the container interior when filling the metering container.
For generating the filling process, at the air-permeable membrane an air pressure differential is applied that generates underpressure in the interior of the metering container through the membrane. By means of this underpressure, the powder is sucked from the filling line into the metering container. The membrane is of such a fine-pore structure that air can pass through it for generating the underpressure but that the powder that is entering the interior of the metering container is retained and remains within the interior.
The illustrated assembly has proven successful for filling of the metering container up to the rim. The individual quantities of the powder can be exactly metered. The rim that circumferentially surrounds the fill opening is covered by the membrane during the filling process so that no powder can deposit thereon. The rim can be used without requiring further cleaning action as a seal surface for the later sealing action of the metering container with a heat sealing film.
A problem in this context is however the design of the permeable membrane. Its capillaries can become clogged in case of certain powder compositions so that a correspondingly complex membrane configuration is required. Powder particles that are jammed in the capillaries entail the risk of so-called cross contamination wherein adhering particles are entrained jointly with the membrane and may mix with deviating powder formulations.
Often, there is moreover the need to fill in a precisely metered powder quantity that however does not completely fill the interior of the metering container. Rather, in certain applications it may be required to allow for a certain air volume in the interior of the metering container in addition to the metered powder quantity. This is however difficult to achieve with the aforementioned membrane filling device because the powder quantity entering the interior of the metering container is sucked against the inner surface of the permeable membrane and therefore a filling up to the rim of the metering container is generated.
The object of the invention is to further develop a filling assembly of the aforementioned kind in such a way that its spectrum of use is expanded while a simplified configuration and reliable operation are provided.